Comparison of batch sorption tests, pilot studies, and modeling for estimating GAC bed life

Area of Science:

• Environmental Science
• Water Treatment Technology
• Microbial Ecology

Background:

• Saint Paul Regional Water Services (SPRWS) faces annual taste and odor issues linked to cyanobacteria-produced geosmin.
• Geosmin contamination occurs in source water from the Mississippi River, conveyed through a lake system.

Purpose of the Study:

• To evaluate the geosmin removal performance and bed life of granular activated carbon (GAC) filter-sorbers.
• To compare pilot-scale experimental data with model simulations for GAC filter performance prediction.

Main Methods:

• Batch adsorption isotherm experiments were conducted.
• Pilot-scale GAC column experiments were performed.
• AdDesignS model simulations were utilized to estimate bed life.

Main Results:

• Batch isotherm parameters estimated GAC bed life between 920-1241 days at 100 ng/L geosmin.
• AdDesignS model simulations predicted a bed life of 594 days.
• Pilot-scale data showed actual bed life exceeding 714 days, attributed to biological geosmin degradation.

Conclusions:

• Biological degradation significantly extends GAC filter bed life, surpassing model predictions.
• The establishment of geosmin-degrading microbial communities in full-scale systems with intermittent loading remains uncertain.
• Careful consideration of both adsorption and biodegradation is crucial for accurately predicting GAC filter bed life in real-world applications.